The present invention relates to a chip card equipped with an open loop antenna, particularly a chip card of the so-called xe2x80x9cmixed connectionxe2x80x9d type, which will be defined below.
Within the framework of the invention, the term xe2x80x9ccardxe2x80x9d should be understood in its most general sense: smart card, xe2x80x9cchipxe2x80x9d Integrated Circuit (I.C.) card, card, etc.
In terms of the mode of communication with the outside world, there are two main categories of chip cards: chip cards with chip cards and contacts without contacts. In the second case, various methods can be used to establish communication between the card and the outside world. It is possible to use, in particular an optical coupling or an electromagnetic coupling by means of a spiral loop antenna. The invention relates to the second type of coupling.
The majority of chip cards are of the first type, i.e., contact cards. These chip cards are made from xe2x80x9cmicromodules,xe2x80x9d i.e. packages comprising a printed circuit or a metal grid having contacts to which integrated circuit componentsxe2x80x94memories, microprocessors, microcontrollers, etc.xe2x80x94are bonded and wired. These components are then protected by a coating resin in order to make the micromodules usable for the final mounting operation. The latter consists of bonding the micromodules into a plastic support comprising a cavity designed to receive this micromodule.
Cards of the second type, called xe2x80x9ccontactlessxe2x80x9d cards, are coupled with the outside environment by electromagnetic induction. The frequencies used are divided into two ranges: a low frequency range, the nominal frequency typically being 125 kHz, and a high frequency range, the nominal frequency typically being 13.56 MHz. For this purpose, an antenna is provided, which normally exists in the form of a spiral loop, connected by its ends to the aforementioned micromodule. In order to obtain adequate sensitivity, it is necessary to provide an antenna comprising about a hundred coils if working at low frequency and 2 to 3 coils if working at high frequency.
The current technologies used for the production of chip cards make it possible to integrate the aforementioned antennas into the material of the chip card, more precisely between two layers of plastic material. The coils are actually disposed on layers of plastic material of the xe2x80x9cPVCxe2x80x9d or xe2x80x9cPETxe2x80x9d type. The metal layers can be printed on the plastic (for example by serigraphy) or produced by depositing a metal lead, produced directly by thermal soldering on the plastic layer.
Finally, there are so-called xe2x80x9cmixedxe2x80x9d chip cards, which constitute the preferred field of application of the invention. This type of chip card has the advantage of allowing access both via xe2x80x9cconventionalxe2x80x9d contacts, which makes it possible to use them in standard readers, or by passing in proximity to suitable transmitting-receiving devices, the micromodules comprising a high-frequency interface. The term xe2x80x9creaderxe2x80x9d should be understood in a general sense, i.e. a device that allows the reading and/or writing of digital information in a chip card.
In the following, we will consider this preferred application, i.e. the case of xe2x80x9cmixedxe2x80x9d chip card.
Generally, chip cards are standardized and comply with certain standards, from both an electrical and a mechanical point of view, particularly the following standards:
ISO 7816 for contact chip cards
ISO 14443 for contactless proximity chip cards.
In the latter case, the frequency used is generally equal to 13.56 MHz, which reduces the size of the antenna, the latter comprising only two or three coils.
The availability of components for xe2x80x9cmixedxe2x80x9d chip cards has lead to the design of novel assembly processes. Keeping in mind that this type of component is mass produced, it is necessary for the final cost price to be as low as possible. Moreover, it is also necessary to obtain high reliability, as in the case of a conventional contact chip card.
For all these reasons, it is desirable to continue to use, insofar as possible, assembly processes and technologies of the prior art that have been tried and tested. Among these processes are the following, to give a non-exhaustive list:
the mounting of the semiconductor micromodule onto a substrate of the printed circuit type, equipped with galvanic contact pads;
the production of the plastic support of the chip card itself, by pressing a stack of layers of plastic material; and
the mounting by bonding of the micromodule into a cavity of the plastic support.
It is still necessary, however, to connect the semiconductor component or xe2x80x9cchipxe2x80x9d to the antenna, and more precisely to the ends of the antenna, which poses a specific problem. The connection is produced via connection pads that must be connected to the aforementioned ends.
In the prior art, it has been suggested that this connection be produced by means of a printed circuit that is two-sided, i.e. comprising metal tracks, for example made of copper, on both sides of an insulating substrate. The substrate in this case is a two-sided printed circuit. The solution has the drawback of a high cost. Because of this, it does not meet at least one of the requirements mentioned.
Furthermore, even if a high frequency is used (typically 13.56 MHz), the antenna is constituted by an open loop, generally comprising at least two or three coils. Therefore, at one point or another on the surface of the chip card, there is necessarily a crossing of two conductive tracks, directly over one another. It follows that it is necessary to provide an insulating area and a conductive xe2x80x9cbridgexe2x80x9d between two antenna sections.
The main object of the invention is to provide an optimized connection that makes it possible to connect the conductive pins of the micromodule of the chip card to the ends of the antenna. It makes it possible, in particular, to minimize the number of metal layers, either at the micromodule level or at the antenna level. It is preferably applied to chip cards of the xe2x80x9cmixedxe2x80x9d type.
For this reason, according to an essential characteristic of the invention, the active side of the substrate carrying the integrated semiconductor component, i.e. the contact pad side, is used to establish electrical connections between input/outputs of the component and coupling antenna terminations.
In a second embodiment, contact pads on the active side of the substrate are also used to establish electrical connections between antenna sections.
The subject of the invention is a chip card comprising a basic body of electrically insulating layers, the card carrying on one of its layers an open loop antenna having two ends, said body being equipped with a cavity housing a micromodule designed to be connected to said open loop antenna by two terminals, said micromodule comprising an electrically insulating substrate carrying, on a first side, a semiconductor component, and on a second side, several electrical contact pads, characterized in that two contact pads are disposed in a strip running through a center region of the substrate, said terminals respectively being connected to said two contact pads through said substrate, the two contact pads respectively being connected to the two ends of the antenna.
The invention also relates to a micromodule designed to be connected by two terminals to an open loop antenna outside the micromodule and having two ends, said micromodule comprising an electrically insulating substrate carrying, on a first side, a semiconductor component, and on a second side, several electrical contact pads, characterized in that two contact pads are disposed in a strip running through a center region of the substrate, said terminals respectively being connected to said two contact pads through said substrate, the two contact pads being designed to be respectively connected to the two ends of the antenna.
Finally, the invention relates to a method for producing a chip card comprising an antenna having two ends, from at least two layers of electrically insulating material, and from a micromodule comprising an electrically insulating substrate carrying, in a center region and on a first side, a semiconductor component, and in a peripheral region and on the first side or a second side, two contact pads connected to two antenna input/output terminals of the semiconductor component, the contact pads being disposed in such a way that once the micromodule is applied to the card, the two contact pads face said ends of the antenna, comprising the following steps:
preparing a first layer carrying said antenna on one side;
preparing a second layer having two through-holes disposed so that once the second layer is applied to the side of the first layer carrying the antenna, said holes face said ends of the antenna;
applying and attaching the second layer to the side of the first layer carrying the antenna;
applying the micromodule to the card so that its semiconductor component is housed in a center well formed in the card, and so that its peripheral region is housed in a peripheral well disposed around the center well;
connecting the contact pads of the micromodule and the ends of the antenna to one another.